Children's Cancer Study Group is engaged in carrying out clinical research programs which have been developed by senior investigators in the group to improve the care and survival of children with acute leukemia and solid tumors. The current protocol study for acute lymphocytic leukemia involves treating high risk patients, i.e., those with white blood counts over 20,000, or those with mediastinal masses, with more aggressive chemotherapy for induction, intensification, and the first year of maintenance. High risk patients are being divided to receive either the same therapy as low risk patients or more aggressive approach, in order to provide controls. Treatment for acute granulocytic leukemia involves the use of five drugs for induction of remission, and the use of immunotherapy with leukemic cells and BCG with chemotherapy for maintenance. Half the patients will be controls and receive chemotherapy only. Solid tumor studies involve those for Wilm's tumor, localized and disseminated neuroblastoma, Ewing's sarcoma, rhabdomyosarcoma, and medullo-blastoma. Protocol studies are being devised for osteogenic sarcoma, histiocytosis, and Grade III - IV astrocytomas.